My laboratory studies signal transduction pathways that regulate growth and programmed cell death in epithelial cancer cells, with a focus on breast and ovarian cancer. Human epithelial malignancies frequently display deregulated tyrosine kinase activity. Understanding the mechanisms that regulate signaling by these kinases should uncover new ways to inhibit cancer cell growth. We are investigating the function of Cbl proteins, a family of proteins that regulate tyrosine kinase activity. Cbl proteins belong to the RING finger class of ubiquitin protein ligases (E3s) and function as E3s for activated tyrosine kinases. My group cloned two of the three mammalian Cbl genes (Cblb and Cblc) and demonstrated that all mammalian Cbl proteins mediate ubiquitination and degradation of the activated epidermal growth factor receptor (EGFR) as well as other components of the signaling complex. Ongoing work is focused on understanding the biochemical and physiologic functions of the three mammalian Cbl proteins in epithelial cells and elucidating the differences in their specificity and/or function. We have been focused on the function of Cblc, the most recently identified family member about which the least is known. This protein is expressed only in epithelial cells and my group is particularly interested in epithelial malignancies such as breast cancer. Previously, to understand the function of the Cblc protein, we collaborated with Josef Penninger (IMBA, Vienna, Austria) to knock out Cblc. Unfortunately, the Cblc null mice have no detectable abnormalities. To gain insight into the fucntion of Cblc, we have used yeast two-hybrid screens to detect novel proteins that interact with Cblc. Currently, we are characterizing the function of these proteins and the consequences of their interactions with Cblc.